//! Trigger-framework tunables. Defaults match design notes §3 (retry
//! policy) and §4 (retention). Each knob is env-overridable via a
//! `PICLOUD_*` variable following the same `tracing::warn` on parse
//! error pattern `SandboxCeiling::from_env` uses.

use std::env;

use serde::{Deserialize, Serialize};

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "lowercase")]
pub enum BackoffShape {
    Exponential,
    Linear,
    Constant,
}

impl BackoffShape {
    #[must_use]
    pub const fn as_str(self) -> &'static str {
        match self {
            Self::Exponential => "exponential",
            Self::Linear => "linear",
            Self::Constant => "constant",
        }
    }

    #[must_use]
    pub fn from_wire(s: &str) -> Option<Self> {
        match s {
            "exponential" => Some(Self::Exponential),
            "linear" => Some(Self::Linear),
            "constant" => Some(Self::Constant),
            _ => None,
        }
    }
}

#[derive(Debug, Clone, Copy)]
pub struct TriggerConfig {
    /// Maximum `cx.trigger_depth` before the dispatcher refuses
    /// execution. Above this, the row is dropped + a metric bumped;
    /// it is NOT dead-lettered (design notes §4: depth-exceeded
    /// means "you built a loop"). Default 8.
    pub max_trigger_depth: u32,

    /// Default retry attempts (per-trigger override on the row).
    pub retry_max_attempts: u32,
    pub retry_backoff: BackoffShape,
    pub retry_base_ms: u32,
    /// ±jitter as a percentage of the computed delay. Applied at
    /// dispatch time — not per-trigger.
    pub retry_jitter_pct: u32,

    /// dead-letter retention before GC, in days. Default 30.
    pub dead_letter_retention_days: u32,
    /// abandoned-execution retention before GC, in days. Default 7.
    pub abandoned_retention_days: u32,

    /// Cron scheduler poll cadence, in ms (v1.1.4). Default 30 000 —
    /// real-world cron precision is per-minute, so a 30s tick is fine.
    /// Floored at 1s by the scheduler.
    pub cron_tick_interval_ms: u32,
}

impl TriggerConfig {
    #[must_use]
    pub const fn conservative() -> Self {
        Self {
            max_trigger_depth: 8,
            retry_max_attempts: 3,
            retry_backoff: BackoffShape::Exponential,
            retry_base_ms: 1000,
            retry_jitter_pct: 20,
            dead_letter_retention_days: 30,
            abandoned_retention_days: 7,
            cron_tick_interval_ms: 30_000,
        }
    }

    #[must_use]
    pub fn from_env() -> Self {
        let mut c = Self::conservative();
        load_u32(&mut c.max_trigger_depth, "PICLOUD_MAX_TRIGGER_DEPTH");
        load_u32(
            &mut c.retry_max_attempts,
            "PICLOUD_TRIGGER_RETRY_MAX_ATTEMPTS",
        );
        load_backoff(&mut c.retry_backoff, "PICLOUD_TRIGGER_RETRY_BACKOFF");
        load_u32(&mut c.retry_base_ms, "PICLOUD_TRIGGER_RETRY_BASE_MS");
        load_u32(&mut c.retry_jitter_pct, "PICLOUD_TRIGGER_RETRY_JITTER_PCT");
        load_u32(
            &mut c.dead_letter_retention_days,
            "PICLOUD_DEAD_LETTER_RETENTION_DAYS",
        );
        load_u32(
            &mut c.abandoned_retention_days,
            "PICLOUD_ABANDONED_EXECUTIONS_RETENTION_DAYS",
        );
        load_u32(
            &mut c.cron_tick_interval_ms,
            "PICLOUD_CRON_TICK_INTERVAL_MS",
        );
        c
    }
}

impl Default for TriggerConfig {
    fn default() -> Self {
        Self::conservative()
    }
}

fn load_u32(dst: &mut u32, key: &str) {
    if let Ok(v) = env::var(key) {
        match v.parse::<u32>() {
            Ok(n) => *dst = n,
            Err(e) => {
                tracing::warn!(env = key, error = %e, "ignoring invalid trigger-config value");
            }
        }
    }
}

fn load_backoff(dst: &mut BackoffShape, key: &str) {
    if let Ok(v) = env::var(key) {
        match BackoffShape::from_wire(&v) {
            Some(b) => *dst = b,
            None => {
                tracing::warn!(
                    env = key,
                    value = %v,
                    "ignoring invalid trigger-config backoff shape (use exponential|linear|constant)"
                );
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn conservative_defaults_match_design_notes() {
        let c = TriggerConfig::conservative();
        assert_eq!(c.max_trigger_depth, 8);
        assert_eq!(c.retry_max_attempts, 3);
        assert_eq!(c.retry_backoff, BackoffShape::Exponential);
        assert_eq!(c.retry_base_ms, 1000);
        assert_eq!(c.retry_jitter_pct, 20);
        assert_eq!(c.dead_letter_retention_days, 30);
        assert_eq!(c.abandoned_retention_days, 7);
        assert_eq!(c.cron_tick_interval_ms, 30_000);
    }

    #[test]
    fn backoff_round_trips() {
        for shape in [
            BackoffShape::Exponential,
            BackoffShape::Linear,
            BackoffShape::Constant,
        ] {
            assert_eq!(BackoffShape::from_wire(shape.as_str()), Some(shape));
        }
        assert_eq!(BackoffShape::from_wire("garbage"), None);
    }
}